I have a newer Cat 299D3XE with the high flow, my ac blows cold but does not blow out at a high speed like it used to Fan speed is at highest setting, when on it hums very loudly and vibrates bad i have cleaned out the filters 2 within a few hours of each other and cleaned out the lines as best as i could, still no air flow Any advice helps! it’s too hot for all this
have you checked the condition of the fan or checked if maybe something in fan to make it unbalanced/plugged
Time for a full disassembly of the aircon/heater assembly and clean out all the nooks & crannies in that case.